Excavation machines, for example hydraulic excavators, wheel loaders, and front shovels operate according to known cycles to excavate and load material onto nearby haul vehicles at a worksite. A typical cycle includes a dig segment, a move-to-truck segment, a dump segment, and a move-to-trench segment. During each of these segments, the excavation machine performs differently and is subjected to different loads. For example, during the dig segment, high forces are required to push an empty tool into the material, while during the move-to-truck segment, high accelerations and high velocities are required for use with a loaded work tool. During the move-to-trench segment, lower accelerations and high velocities are required for use with an empty work tool.
The engine speed of the excavation machine is set by an operator, and can be affected by loading. For example, the operator sets the speed of the engine to a desired speed (e.g., to high-idle) at the start of the excavation cycle, and the actual speed of the engine may droop under or shoot over the desired speed according to loading of the work tool and/or movement of the machine over different grades at the worksite. Specifically, when high forces and/or accelerations are suddenly placed on the machine (e.g., during the dig segment, the move-to-truck segment, or travel up a steep grade), the engine speed may droop. And when the forces are suddenly removed (e.g., during the dump segment, move-to-trench segment, or travel down a steep grade), the engine speed may overshoot.
Engine speed fluctuations can result in reduced responsiveness, low production, and/or inefficiencies. In particular, when engine speed droops, the engine may not immediately produce the power necessary to move the work tool and load in the manner requested by the operator. In addition, at low engine speeds, an amount of combustion air provided to the engine by associated turbochargers may also be low, thereby limiting an amount of fuel that can be supplied to the engine. This fuel limit can result in a lag or delay in how quickly the engine can speed back up to the desired speed. In addition, the desired speed is often a speed at which engine efficiencies (e.g., fuel efficiency and/or exhaust emission efficiency) are heightened. Accordingly, deviations from the desired speed can result in undesired performance.
One way to improve engine performance of a machine during an excavation cycle is disclosed in U.S. Pat. No. 8,374,755 of Lin et al. that issued on Feb. 12, 2013 (“the '755 patent”). Specifically, the '755 patent discloses an excavation machine control system having a power source, an operator interface device configured to generate a signal indicative of a desired mode of power source operation, a work implement driven by the power source, and a controller. The controller is configured to classify a currently performed task and select an output map based on the classification and the desired mode of operation. The controller is further configured to control the power source using the output map, such that fuel efficiency and exhaust emissions are improved.
Although the control system of the '755 patent may improve engine performance, the system may still be less than optimal. In particular, the system may not consider all factors affecting engine performance or be able to adapt to changing performance over a life of the machine.
The disclosed control system is directed to overcoming one or more of the problems set forth above and/or other problems in the prior art.